Support is requested for continuation of research aimed at developing a clinical method for prediction of functional success in the use of telescopic spectacle aids by low vision patients (LVP). Results to date indicates that failure to benefit from these expensive aids is associated most strongly with 1) increased sensitivity of visual acuity to head movement and 2) excessive spontaneous head oscillations. These two factors alone, measured under laboratory conditions, prospectively predict functional success or failure of motivated telescope wearers with about 80% accuracy. Failure is thought to be due to excessive loss of visual acuity during involuntary head movements present in everyday life. Presently, low vision clinicians evaluate the efficacy of head borne telescopic devices with the patient seated, often with the head supported by a headrest. Thus the factors which could potentially cause failure due to a severe reduction in visual acuity during normal activities are not considered in low vision evaluations. The general goal of the proposed research remains the development of a quantitative basis for prediction of telescope use by LVP's. Specific aims include: 1) refining the accuracy of the predictive formula by basing it on a broader base of LVP's; 2) developing a predictive formula and test procedures for LVP's with nystagmus; and 3) developing simplified techniques for the clinical measurement of the predictive factors. To achieve this goal, a large broad based ample of LVP's with and without nystagmus will be evaluated using precise laboratory techniques including measurements of head stability (HS), dynamic visual acuity (DVA), vestibulo-ocular reflex and visual vestibulo-ocular reflex plasticity. HS will quantify involuntary head oscillations during natural activities such as standing and walking. DVA will quantify acuity during head movement. Simplified methods designed for clinical use will be developed and tested alongside the full laboratory procedures Statistical predictive functions based on such measurements will be prospectively validated separately for patients with and without nystagmus. Independent, certified orientation and mobility specialists, who will be "blind" to prediction, will provide an objective evaluation of whether or not a patient is using telescopes successfully in daily tasks. A predictive formula based on simple measurements in the low vision clinic will assist the clinician in prescribing telescopic spectacles and will improve rehabilitation strategies.